Method and apparatus for defeating ballistic projectiles

ABSTRACT

A method and apparatus for defeating high-velocity projectiles. A plurality tile are retained in an imbricated pattern row by row such that each disk in a row is in substantially a straight line with the other disks in the row and overlaps a segment of a disk in an adjacent row. The imbricated pattern is then adhered to a flexible, high tensile strength substrate and overlaid by a second high tensile strength layer such that the imbricated pattern is enveloped between the substrate and the second layer. The envelope is then coupled to a soft body armor backing.

This patent application is a continuation of pending divisional patentapplication Ser. No. 10/859,697, filed Jun. 2, 2004, entitled METHOD ANDAPPARATUS FOR DEFEATING BALLISTIC PROJECTILES, which is a divisional ofissued U.S. Pat. No. 6,745,661 issued on Jun. 8, 2004 entitled METHODAND APPARATUS FOR DEFEATING BALLISTIC PROJECTILES, which is acontinuation of issued U.S. Pat. No. 6,035,438 issued Mar. 14, 2000entitled METHOD AND APPARATUS FOR DEFEATING BALLISTIC PROJECTILES.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to protective wear. More specifically, theinvention relates to flexible body armor designed to defeathigh-velocity projectiles.

2. Background

Advances in body armor are frequently related to development of improvedmaterials from which the armor is formed. In recent years, ballisticresistant materials formed from high tensile strength fibers, such asaramid fibers or polyethylene fibers, have gone into common use in thefield. Unfortunately, soft body armor, even with these advancedmaterials, has proven insufficient to thwart even armor-piercing pistolammunition, sharp thrusting implements, and circular penetrators, all ofwhich are now in common use.

To address this problem, various hard metal plating systems have beendeveloped. One such system employs a number of titanium disks one inchin diameter and having a uniform thickness in the range of 0.032-0.050inches in thickness laid out in overlapping rows such that in theinterior of a row, a disk overlaps its predecessor in the row and isoverlapped by its successor in the row. Subsequent rows overlap theirpredecessor and are overlapped by their successor. The coin layout isthen attached to a substrate such as adhesive impregnated aramid fabric.A second layer of adhesive impregnated aramid may be used to envelopethe “plate” formed by the coins. This enveloped plate can be attached toconventional soft body armor over vital organs. It provides goodflexibility and is thin enough to conceal.

While this overlapping of the coins has been shown to spread the forceeffectively to defeat most existing armor-piercing pistol rounds, sharpthrusting implements, and circular penetrators, unfortunately, riflerounds continue to tear through this plating structure (even when setout in an imbricated pattern), as well as the underlying soft body armorlike a hot knife through butter. Thus, for protection from rifle rounds,users have been required to employ large rigid plates to shield thevital organs. These large plates are heavy and inflexible, and generallyuncomfortable to use. Additionally, they are next to impossible to usein a concealed manner. Efforts to employ the coin design with thickerdisks have failed to yield a commercially viable product to defeat riflerounds. Thicker disks result in less flexibility and do not lay outwell. The result is a plating structure thicker, no more flexible, andheavier than the solid plates discussed above. Wearer comfort is also apremium concern in body armor production. Accordingly, these limitationsmake such a structure impractical as a commercial product.

In view of the foregoing, it would be desirable to have a flexiblearmoring system that would defeat high-velocity projectiles, such asrifle rounds.

BRIEF SUMMARY OF THE INVENTION

A method and apparatus for defeating high-velocity projectiles isdisclosed. A plurality of tiles are laid out in an imbricated patternrow by row such that each disk in a row is in substantially a straightline with the other disks in the row and overlaps a segment of a disk inan adjacent row. The imbricated pattern is then adhered to a flexible,high tensile strength substrate and overlaid by a second high tensilestrength layer such that the imbricated pattern is enveloped between thesubstrate and the second layer. The envelope is then coupled to a softbody armor backing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a frontal view of one embodiment of body armor.

FIG. 2 is a cutaway view of one embodiment of the body armor.

FIG. 3 is a side cutaway cross-sectional view of one embodiment of thebody armor.

FIG. 4 is a perspective view of one disk embodiment.

FIG. 5 is a perspective view of the disk embodiment of FIG. 4 with anepoxy modified resin and Eglass coating.

FIG. 6 is a sectional view of the disk embodiment of FIG. 5 illustratingthe coatings.

FIG. 7 is a perspective view of one disk embodiment.

FIG. 8 is a sectional view of one disk embodiment.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a frontal view of a suit of body armor as worn in oneembodiment of the instant invention. The body armor 10 covers a user'storso and is designed to protect the vital areas from high-velocityprojectiles. Flaps 20 on the body armor extend around the wearer's bodyto extend protection to the wearer's sides. In one embodiment the bodyarmor wraps around a segment of the wearer, for instance the torso,providing substantially uniform armor protection in a envelopingcircumference.

FIG. 2 is a cutaway frontal view of one embodiment of a suit of bodyarmor. Disks 52 are arrayed in an imbricated pattern to cover vitalareas where the body armor is worn. Unlike the 10×12 rigid plates of theprior art, the imbricated pattern can flex around body contours and istherefore considerably more comfortable and also more readilyconcealable. Each disk 52 is formed of a high hardness material. In oneembodiment, each disk is discus shaped having a maximum thickness in thecenter of the disk and declining in thickness towards the outer edge byproviding one or more downwardly inclined surface segments. In oneembodiment, the thickness of the discus shaped disk declines in auniform downward inclined slope from the center towards the outer edge.In another embodiment the discus shape has an internal circumferencewithin which the disk is uniformly thick and slopes uniformly downwardbetween the internal circumference and the circumferential edge of thedisk.

Typically, the edge thickness will be approximately one-half thethickness in the center. As such, when laid out in the imbricatedpattern the disks exhibit a pivot capability which allows on the orderof 60% greater flexibility than metal plates or existing coinarrangements. Many such suitable ceramic materials exist which are alsoof relatively lighter weight when compared to steel or other highhardness metals.

The tapering design intrinsic to the discus shape of one embodiment ofthe invention renders the disk surface non-planar, providing a slope todeflect ballistic impacts as compared with a uniform flat planarsurface. In this regard, the ceramic composite material can be sinteredand/or molded into a homogenous ballistic grade discus shape more easilyand less expensively than can a metal disk, which must either be lathedor tooled to produce a similar tapering discus form. However, discusshaped metal disks are within the scope and contemplation of theinvention. Through appropriately laying out disks in an imbricatedpattern, the overall body armor 10 remains flexible and also providesgood protection against high velocity projectiles.

Additionally, the lighter weight and greater flexibility of the ceramiccomposite as compared to prior art protection from high velocityprojectiles, allows for greater mobility and range of motion by thewearer. For instance, body armor vests composed of imbricated ceramicdisks of ballistic grade hardness and fracture toughness may wrapentirely around a segment of the wearer, for instance the torso,extending disk protection up to 360 degrees about the wearer. Thelighter ceramic material also avoids pronounced negative buoyancy ofhigh hardness metal coins or plates typical of prior art body armor.This provides for climbing or swimming uses in the field for which priorart body armor is not suitable.

The imbricated pattern 12 is typically sandwiched between two layers offabric 14 made of high tensile strength fibers, such as aramid fibers orpolyethylene fibers. The fabric 14 should be tear and cut resistant andis preferably ballistic grade material designed to reduce fragmentation.This fabric 14 can be adhesive impregnated, thus, the adhesive on thefabric adheres to the disks that compose the imbricated pattern 12 andretains their relative position. One or more additional layers of thefabric 14 may be added to the sandwich. This will be discussed furtherbelow.

Underlying the imbricated pattern of disks 52 that is sandwiched betweentwo or more layers of tear and cut resistant fabric layers 14 isconventional soft body armor 16. A high-velocity projectile is deemeddefeated even if it penetrates the disks of the imbricated pattern andall fabric layers if it does not penetrate the underlying soft bodyarmor or cause backside deformation of greater than 1.73″, as backsidedeformation is defined by the National Institute of Justice (NIJ). Inone embodiment, multiple layers of fabric are added to the side betweenthe ceramic disks and the wearer as additional protection againstbackside deformation and to catch projectiles and fragments thereof.Attachment straps, such as strap 18, connect the armor to a bodysegment, for instance the shoulders, to provide additional support.Attachment strap 18 could be any conventional strapping common in theindustry.

To arrange the imbricated pattern, the disks are laid out from left toright. Each subsequent row is also laid out left to right. It has beenfound that switching from left to right, then to right to left, createsweakness in the resulting pattern that often causes failure. Diskswithin each row form a substantially straight horizontal line. Becausethe disks overlap, each disk lies on a slight tilting slope relative toa line normal to the horizontal layout surface. In one embodiment, thisslight slope of the disks complements their inclined discus shape toincrease the probability of impact deflection.

After the disks are laid out from left to right and top to bottom andsandwiched between a pair of adhesive layers, the entire pattern isinverted for assembly into body armor. It has been found that themajority of threats arrive at a downward trajectory. Thus it isdesirable that each row of disks overlap the row below it as the armoris worn. It is, however, within the scope and contemplation of theinvention to lay out the disks in an alternative order, e.g. right toleft, bottom to top. It is also contemplated that inverting theimbricated pattern in the course of assembling the body armor may beconnected such that each row overlaps the row above it.

A number of possible ceramic composites have been found suitable as highhardness materials for the disks. These include fiber induced ceramicssold under the trademarks SINTOX® FA and DERANOX® by Morgan Matroc, Ltd.of Bedforshire, England. In particular, SINTOX® FA alumina oxide ceramicand DURANOX® D995L, for a zirconia toughened alumina oxide ceramiccomposite, composed of approximately 88% by weight alumina plusapproximately 12% by weight transformation toughened zirconia (TTZ),have proven suitable ceramic composites.

While alumina based composites are preferred, other bases may beutilized to form the ceramic composite including barium titanate,strotium titanate, calcium zirconate, magnesium zirconate, siliconcarbides and boron carbides. As indicated, these potential ceramic basesare not limited to oxide ceramics but also include mixed oxides,non-oxides, silicates as well as MICATHERM® ceramics, (the latter beinga trademark for inorganic thermoplastic materials sold by Morgan Matroc,Ltd, of Bedforshire, England).

Suitable ceramic composites would have relatively high hardness andfracture toughness. Typically, such materials would have at leastapproximately 12 GPa in hardness and at least 3.5 MPa m^(1/2) infracture toughness in order for the armor to withstand a level threeballistic event as defined by the National Institute of Justice (NIJ). Alevel three threat is a full metal jacket 7.62×51 mm 150 grain roundtraveling at 2700-2800 ft./sec. Ultimately, hardness and fracturetoughness levels will depend on the type of ceramic composite employed.For exemplary embodiments of the present invention using alumina bases,the fracture toughness minimum for alumina would be 3.8 MPa m^(1/2) and4.5 MPa m^(1/2) for zirconia toughened alumina. The hardness for aluminawould be in the approximate range of 12 to 15 GPa, and for zirconiatoughened alumina, the hardness would be at least approximately 15 GPa.

In certain instances, the ceramics employed may be supplemented by theaddition of a toughening agent such as toughened metallic oxides. In oneembodiment, TTZ is added to the alumina base. The inclusion of metallicoxides increase the strength of the resulting ceramic composite andresist disassociation of the disk upon impact during a ballistic event.For alumina based ceramic composites, the range of TTZ percentage byweight for suitable ballistic grade ceramics would be between 0.05% and20%. In one embodiment the percentage of TTZ by weight to the aluminabase is approximately 12% of the composite.

The ceramics are mixed in ways commonly known in the art. Sintering andmolding, including injection molding, methods to form the disk are wellknown in the art. In one embodiment, the disks may be formed byinjection molding and then pressing to the desired shape. Once formed,certain embodiments of the disks are then encompassed with a containmentwrap material. This material provides greater integrity to the disk andincreases its fracture toughness, consequently enhancing its ability toabsorb the impact of ballistic projectiles without disassociation. Inone embodiment, this wrap is a glass fiber wrap adhered by an adhesivesubstrate. Suitable glass fiber materials include Eglass and S-2 Glassavailable from Owens Corning Fiberglas Technology, Inc. of Summit, Ill.Suitable adhesives include modified epoxy resins. The containment wrapand epoxy resin substrate can be applied to the disk by autoclaving, orin other ways known to the art. Strength, cohesion and structuralintegrity may also be imparted by overlaying the disk surface witharamid fibers, layered or cross-laid on an adhesive substrate.

Typically, disk 52 has a radius between ½″ and 1″. Longer radii reduceflexibility but also manufacturing cost. In a current embodiment, a 1″radius is employed. Each disk tapers in thickness varying between itscenter region (where the thickness is at its maximum) and its edge(where the thickness is at a minimum). Maximum and minimum thicknesseswill vary according to the level of ballistic threat to be defeated. Forinstance, to defeat a high velocity rifle ballistic threat, a maximumthickness of ⅜″ in the center tapering to 3/20″ minimum thickness at theedge may be used. A low velocity rifle threat (or a high velocity pistolthreat) may only require a thickness of between ⅛″ (maximum) and 1/10″(minimum). In one embodiment, the discus shaped disks have a centerthickness of approximately ¼″ and an edge thickness of ⅛″.

The overlap of the imbricated placement pattern has been found toeffectively spread the force of a high-velocity projectile hit toadjacent disks, thereby preventing penetration and backside deformation.Additionally, because of the slight tilt of each overlapping disk in theimbricated pattern, a perpendicular hit is very unlikely and some of theenergy will be absorbed in deflection. In the discus embodiment, thetapering of thickness, forming a non-planar inclined surface renders aperpendicular strike extraordinarily unlikely.

FIG. 3 shows an imbricated pattern of disks 52 coupled to a substrate.As previously discussed, substrate could be an adhesive impregnatedpolyethylene or aramid fiber fabric. Suitable fabrics include the fabricsold under the trademark SPECTRA® by AlliedSignal of Morristown, N.J.,TWARON® mcrofiliment by Akzo-Nobel of Blacklawn, Ga., SB31 and SB2, soldunder the trademark DYNEEMA, by DSM of Holland, PBO sold under thetrademark ZYLON® by Toyobo of Tokyo, Japan (pursuant to a license fromDow Chemical, Inc. of Midland Mich.), KEVLAR® or PROTERA® by E.I. Dupontde Nemours & Company of Chattanooga, Tenn. Other suitable fabrics willoccur to one of ordinary skill in the art.

Some suitable substrates are available with an aggressive adhesivecoating covered by a release paper. In addition to being aggressive, itis important that the adhesive once cured remains flexible to reduceseparation of the disks and substrate during a ballistic event. Thesubstrate of a desired size may be cut and the release paper peeled backto expose the adhesive surface. The disk can then be laid out directlyonto the adhesive which retains them in position relative to oneanother. Because the substrate is flexible and the disks flex abouttheir intersection, pivoting somewhat within the imbricated layout, thecombined unit is significantly flexible; on the order of 60% moreflexible than the prior art metal plate and coin configuration armor.Alternatively, the pattern may be laid out and the substrate adheredover the top.

The next step is to place another layer of this adhesive coated flexiblesubstrate on the other side of the disks to secure them in a flexibleposition that does not change when the panel is flexed. The actualposition of each disk remains substantially in the same place it waslaid. This second layer of adhesive fabric used to envelop theimbricated pattern provides further staying power, thereby reducing therisk that a disk will shift and the body armor will fail.

It has been found that the above-disclosed invention will defeat a levelthree threat and all lesser threats. Additional layers of the adhesivecoated flexible substrate material may be added to either side in anyproportion (i.e. it is within the scope and contemplation of theinvention to have more substrate layers on one side of the plate thanthe other side of the plate) in multiple layers to achieve differentperformance criteria. Some situations benefit from allowing the disks tomove slightly during the ballistic event, while others make it desirablethat the disk remain as secure in place as possible.

In an alternative embodiment of the invention, a “dry” high tensilestrength flexible substrate is provided. It is then coated with aflexible bonding agent, for example, a silicon elastomer resin. Thedisks may then be laid out as described above. The bonding agent is thencured to flexibly retain the relative locations of the disks. Asimilarly coated layer can be used to sandwich the plate from theopposite side. It is also within the scope and contemplation of theinvention to use one layer with a flexible bonding agent while a facinglayer is of the peel and stick variety described above. As used herein,“adhesive impregnated substrate” refers to suitable flexible hightensile strength material having an adhesive disposed on one side,whether commercially available with adhesive in place or coated later asdescribed above.

In yet another embodiment, an adhesive impregnated substrate is createdby either above described method and the (sandwiching) layer isnon-adhesive and merely coupled to the underlying substrate about theperiphery of the plate. This will somewhat degrade the retention of thedisk as compared to sandwiching between adhesive layers. Accordingly,this configuration will not survive as many hits and the front layerattached about the periphery serves primarily as a spall shield.

FIG. 4 is a perspective view of a disk. In this embodiment, the disk hasa discus shape of varying thickness, ¼″ in the center tapering with auniform slope to ⅛″ at the circumferential edge. In an imbricatedpattern, edges of adjacent disks will overlap, creating areas ofsignificant thickness having multiple disk layers. Ordinarily, thispattern will not overlap the center, or thickest region, of the disk.Thus, a projectile striking the disk pattern at any point will impacteither a singular disk near its thickest region, or multiple layereddisks at least as thick, and likely thicker, than the thickest region ofthe singular disk. Moreover, the slope of the discus shape between areasof varying thickness discourage any perpendicular ballistic impact.

FIG. 5 shows a perspective view of a disk after application of acontainment wrap. As noted above, this wrap may be a fiberglass oraramid fiber composite adhered to a substrate which may be a modifiedepoxy resin. The wrap imparts greater fracture toughness and hardness,reducing disk shatter and disassociation in response to a ballisticevent.

FIG. 6 shows a cross section of a disk illustrating its discus shape.The layers of adhesive 22 and containment wrap 24, as noted above, areevident.

FIG. 7 is a perspective view of a disk of an alternative embodiment ofthe invention. In this embodiment, formation of the disk issubstantially as described above, varying only in the slope of the endresult. While varying in thickness from the center to the edge, theslope of tapering is not uniform, leaving a more pronounced bulgingcenter having a domed shape. This leaves the surface area extending fromthe circumference edge to the domed center substantially planar. Thisembodiment allows for the disks to have a greater overlapped surfacearea, increasing the surface area in which a projectile would encountermultiple layers of disk. However, the substantially planar regionincreases the probability of a perpendicular strike. The domed disks canbe laid out in an analogous manner to that described above and assembledinto body armor capable of defeating level three threats.

FIG. 8 is a side view of the alternative embodiment shown in FIG. 6.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit and scope of the invention as setforth in the appended claims. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense. Therefore, the scope of the invention should be limited only bythe appended claims.

1. A panel for body armor comprising: a plurality of discrete tilesretained in an imbricated pattern such that individual tiles in a layerpartially overlap adjacent tiles in the same layer wherein each tile hasa non-planer threat side face; an adhesive holding the tile in theimbricated pattern; and a plurality of layers of ballistic grade fabricenclosing the layer of tiles.
 2. The panel of claim 1 wherein each tilecomprises a ceramic material having a hardness of greater than 12 GPa.3. The panel of claim 2 wherein the ceramic material is selected fromthe group of silicon carbide and boron carbide.
 4. The panel of claim 1wherein the panel defeats a national institute of justice level threeballistic threat.
 5. The panel of claim 1 wherein at least a portion ofthe threat side face of each tile has a non-linear slope.
 6. The panelof claim 1 wherein each tile comprises: a ceramic material having afractured toughness of at least 3.8 Mpa-m^(1/2).